Introduction
Environmental toxins are common but less studied factors that affect kidney health in vulnerable populations. Almost 26 percent of kidney disorders are induced by environmental toxins. Several environmental risk factors can harm kidney health.
Exposure to environmental toxins during the kidney's developmental phase in fetuses, infants, or childhood can result in chronic kidney disease. The second and third trimesters are critical windows for kidneys, nephrons, and tubule formation, and toxin exposure could influence kidney function and blood pressure.
Therefore, it is necessary to minimize exposure to these environmental toxins. Some measures to avoid toxin exposure are stopping cigarette smoke, reducing air pollution, and preventing exposure to heavy metals.
What Is the Importance of the Kidney in the Human Body?
The kidney helps regulate several vital body functions that are:
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Filtering of blood to excrete various endogenously derived or exogenously acquired toxins. Some toxins eliminated are ammonia, urea, creatinine, toxins produced by phase II hepatic detoxification, and heavy metals.
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Kidneys help balance electrolytes, sodium, potassium, and calcium levels.
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The proximal tubule of the kidneys helps convert the inactive form of vitamin D to the active.
What Are the Environmental Toxins That Affect Kidney Health?
Various toxins encountered in the environment can become toxic to kidneys and include:
Heavy Metals: Metals are common environmental pollutants associated with impaired kidney function.
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Lead (Pb): Common heavy metals are in paints, batteries, gasoline, and the construction industry. The use of this metal in a few industries is being discontinued as it causes kidney disease. Lead circulates in the blood and is eliminated by the kidney or accumulated in bone. Lead exposure from moonshine alcohol is a common phenomenon. Exposure to Pb can induce oxidative stress to glomerular and tubular cells, producing free radicals that cause changes in renal structure and function. Acute toxicity results in proximal tubular injury, whereas chronic poisoning leads to nephropathy, which is always associated with gout and high blood pressure. Additionally, chronic lead exposure at low levels causes chronic kidney disease. Higher blood levels of Pb enhance the risk of developing kidney stones.
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Mercury: Mercury exposure could be through dietary, occupational, and environmental sources. Specific or freshwater fish from contaminated water sources can have high mercury levels. Other food sources include plants, meat, cereals, and water. Combustion of fuel and coal can produce mercury. Electric bulbs, switches, or battery manufacturing workers can be exposed to mercury. Mercury is toxic to the glomerulus and tubules of the kidney. Individuals who use mercury-containing skin-lightening creams have reported membranous nephropathy (inflammation of the glomerulus) and minimal change disease.
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Arsenic: Naturally found heavy metals are present in seafood, groundwater, and pesticides. Woods coated with arsenic, when burnt, can cause exposure with fume inhalation. Arsenic can cause chronic kidney disease, but folk medicine still uses the compound. Other renal disorders are acute tubular necrosis (death of tubular epithelial cells) and tubulointerstitial nephritis (kidney inflammation).
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Cadmium: Cadmium is a known nephrotoxic environmental pollutant. Cigarette smoking and burning household or industrial waste can cause exposure. Contaminated water, liver, kidney meat, or shellfish are potential risks. Workers in smelters, metals, and battery manufacturing industries are exposed. Cadmium exposure can cause chronic kidney disease, kidney stones, and cancer. High levels of cadmium exposure can cause cadmium to accumulate in the proximal tubules in the kidneys, leading to impaired tubular function and protein reabsorption. The classic feature of Itai-Itai disease is kidney failure caused by cadmium toxicity. Cadmium in urine indicates long-term cadmium exposure, whereas cadmium in blood suggests more recent cadmium exposure within a month.
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Uranium: Heavy metal is found in soil, water, and plants. Exposure to uranium can affect the kidneys by increasing calcium and protein levels in urine. In severe toxicity cases, it causes acute kidney failure. Other renal disorders caused by uranium exposure are kidney stones, urinary tract strictures, and bladder disorders.
Aristolochic Acid: Aristolochia is a plant that can grow in different climatic conditions worldwide. The plant is utilized in traditional medicine like Chinese medicine. However, recent studies suggest the plant is toxic to the kidney and is a cancer-causing agent. The plant is classified as a Group 1 carcinogen by the International Agency for Research on Cancer.
Non-metals:
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Phthalates: Phthalates are added to foodstuffs as substitutes for emulsifiers and are present in nutrient supplements and probiotics taken by children. The substance is added to cosmetics as a solvent for fragrance, paint, toys, and medical devices. The most common phthalate exposure in the general population is using plastic containers or bags at high temperatures and plastic use during food production. Humans are exposed to phthalates through inhalation, absorption through the skin, or ingesting food. Phthalates are associated with renal injury.
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Melamine: The substance is found in contaminated milk, plastics, and adhesives. It is known to cause kidney failure and kidney stones.
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Bisphenol A (BPA): Environmental BPA exposure can occur by absorption through skin, ingestion, and respiration. High BPA levels were found in the urine of 93 % of adults, and the serum concentration of the non-metal was increased in men and smokers. Several studies have noted a positive association between BPA levels and chronic kidney disease.
Environmental Pollution:
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Water Pollution: The kidney is a vulnerable target for water pollutants due to its high blood supply and excretory function. Increased sweat loss, intake of large amounts of fluids, and contaminated water supply can expose kidneys to high doses of nephrotoxicants.
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Air Pollution: Air consists of suspended solid and liquid particles known as particulate matter. It is a common air pollutant that varies in size and chemical composition. The composition of the particulate matter includes nitrates, sulfates, ammonium, inorganic ions, metals, and biological agents like allergens and microbial substances. The particulate matter causes health concerns if their size exceeds 2.5 to 10 micrometers.
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Recent studies reveal particulate matter could cause chronic kidney disease by causing a decline in glomerular filtration rate.
Physical Agents Like High Temperature, Heat, or Dehydration: Young men working in mines, docks, brick industries, or trophic countries have reported tubulointerstitial nephritis. The cause is unclear, but few studies suggest hard physical labor in high environmental temperatures could induce heat-related kidney injury.
Conclusion
Environmental factors like heavy metals, air pollution, and non-metals can cause various renal disorders, especially in developing countries where pollution is prevalent. The toxins cause renal damage by initiating inflammation or oxidative stress. Therefore, it is necessary to formulate environmental protection strategies and establish safe exposure levels for pollutants.
